The vast majority of the Earth's sentient beings are AI's that will exist entirely as thinking computer programs capable of instantly moving from one computer to another across the Internet. These computer-based beings will be capable of manifesting themselves at will in the physical world by creating or taking over robotic bodies, with individual AI's also being capable of controlling multiple bodies at once.
Kurzweil, Ray. 1999. The age of spiritual machines: when computers exceed human intelligence. New York: Viking.